This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
IPDC is a broadcast technology which enables cost effective and efficient distribution of digital content to mass audiences. Technically, IPDC makes use of the DVB-T networks to broadcast any IP based data. IPDC over the DVB-H specification defines two different types of delivery methods. These methods comprise file delivery and streaming delivery. The file delivery method is based on the File Delivery over Unidirectional Transport (FLUTE) protocol and allows for the delivery of files as transport objects to the terminal. The FLUTE protocol is discussed in detail at the Internet Engineering Task Force (IETF) website. The file delivery method is used, e.g., for the delivery of the Electronic Service Guide (ESG) data. ESG data announces information about the service and how to obtain access to it at the terminal. Several other services, such as the downloading of music and video clips, may also be realized using the file delivery method.
The streaming delivery method, on the other hand, is used for the realization of streaming services such as Mobile TV and Radio. The streaming delivery method is based on the Real-Time Transport Protocol (RTP) and standard media codecs such as H.264/AVC and MPEG-4 HE AAC. Information on the RTP protocol can be found at the IETF website.
In order for a user to consume an IPDC service, a number steps usually need to be performed. First, the terminal needs to tune in to the ESG bootstrap session, which is located at a well known Internet Protocol (IP) address. The ESG bootstrap session provides information on existing ESG providers and their corresponding ESG sessions. The terminal must then tune to the selected/pre-configured ESG session and retrieve a snapshot of the current ESG data. The user is then offered the opportunity to browse the ESG information and to pick up the service of his or her choice for consumption. The terminal retrieves the respective Acquisition Fragment from the ESG. The Acquisition Fragment contains a description of the different media components of the session, as well as a SDP file that describes how to access the session, the media codecs in use, and other configuration information. Information about the SDP protocol can be found at the IETF website. The terminal then tunes to the IP flows of the service in order to consume the data. The SDP file of the session may be delivered embedded within the Acquisition Fragment, or it may be delivered as a separate item in a FLUTE session. The FLUTE session is described by an embedded SDP file in the Acquisition Fragment.
Some Mobile TV channels may require dynamic and unpredictable modifications to the session configuration. These modifications may be similar to a live TV channel where an additional audio language or a multi-camera view is suddenly made available. In such a situation, terminals in a Mobile TV environment that are consuming the service at the time are typically not aware of the changes, as they are typically not following updates to the ESG. It is possible to deliver updates to the SDP in a FLUTE session that is delivered along with the media streams. However, the new SDP file must still be synchronized to a running session, and there are currently issues as to how the terminal should treat SDP session updates. A dynamic session update, as described herein, refers to the operation by which the SDP file of an ongoing session is replaced by a newer SDP file that is signaled through appropriate mechanisms.
ESG data is typically delivered in a different Elementary Stream, and likely also in a different Transport Stream, than the file delivery and streaming sessions that the ESG data describes. In such a case, a terminal typically updates its ESG database upon tune in, and then switches to the selected stream for service consumption. During service consumption, it is assumed that the terminal is not following updates to the ESG, as this significantly increases the power consumption and may not be possible, for example, in case of different Transport Streams. However, some services, such as a TV channel service, may need to update the ESG in an unpredictable manner. As an example, a new audio language or a subtitling stream may appear suddenly in the TV channel's contents. In another case, a previously scheduled event may be postponed due to various types of delays. In such scenarios, the session description file of the streaming session needs to be updated in order to correctly consume the service. Furthermore, terminals that are consuming the service and are not tuned to the ESG have to be made aware of the changes to the session parameters. The ESG specification (which can be found in “Digital Video Broadcasting (DVB); IP Datacast over DVB-H: Electronic Service Guide (ESG)” ETSI TS 102 471 V1.1.1 (2006-04) at the ETSI website) defines, for the above purpose, an out of band delivery mechanism of the SDP file. A FLUTE session may be used to deliver the most up-to-date SDP file to the terminals that are currently consuming the service or are just tuning in to the service. It is anticipated that the FLUTE session is delivered in the same Elementary Stream as the media streams of the streaming service.